Method SortingTransform

src/Processors/Transforms/SortingTransform.cpp:187–237

SortingTransform::SortingTransform(
    SharedHeader header,
    const SortDescription & description_,
    size_t max_merged_block_size_,
    UInt64 limit_,
    bool increase_sort_description_compile_attempts)
    : IProcessor({header}, {header})
    , description(description_)
    , max_merged_block_size(max_merged_block_size_)
    , limit(limit_)
{
    const auto & sample = inputs.front().getHeader();

    /// Remove constants from header and map old indexes to new.
    size_t num_columns = sample.columns();
    ColumnNumbers map(num_columns, num_columns);
    const_columns_to_remove.assign(num_columns, true);
    for (size_t pos = 0; pos < num_columns; ++pos)
    {
        const auto & column = sample.getByPosition(pos);
        if (!(column.column && isColumnConst(*column.column)))
        {
            map[pos] = header_without_constants.columns();
            header_without_constants.insert(column);
            const_columns_to_remove[pos] = false;
        }
    }

    DataTypes sort_description_types;
    sort_description_types.reserve(description.size());

    /// Remove constants from column_description and remap positions.
    SortDescription description_without_constants;
    description_without_constants.reserve(description.size());
    for (const auto & column_description : description)
    {
        auto old_pos = header->getPositionByName(column_description.column_name);
        auto new_pos = map[old_pos];

        if (new_pos < num_columns)
        {
            sort_description_types.emplace_back(sample.safeGetByPosition(old_pos).type);
            description_without_constants.push_back(column_description);
        }
    }

    description.swap(description_without_constants);

    if (SortQueueVariants(sort_description_types, description).variantSupportJITCompilation())
        compileSortDescriptionIfNeeded(description, sort_description_types, increase_sort_description_compile_attempts /*increase_compile_attempts*/);
}

SortingTransform::~SortingTransform() = default;